Im about to install some tracking fins on my CSX220 and not sure how critical the mounting location is.
Do the X25's come with tracking fins? Or has anybody installed them on a boat that didnt come with them?
Do I need 3 of them?

I put 3 on a 1995 Marristar 225 handling is great, we run it thru the ski course. But 2 fins would have been enough. I purchase but never installed another rudder which I was going to "shave" down a bit. Not to reinvent the wheel but I traced a X2's rudder since the hulls were similar. The smaller rudder would/will help with the "Rudder dance" (very minor and I'm the only one who notices it) at top end. I place one fin directly under the ski pylon and one fore and one aft of that one. I also added a Lenco trim plate and these are the best 2 mods I have done to the boat. I plane 2.5 times quicker then my buddies stock 225 and can turn well inside of him. At full throttle boat will not chine lock in amax effort turn. But you will throw passengers around so be careful. May have been overkill but I placed a common 1/4 aluminum Plate inside to "back the fins". There are no recesses for the fins under the hull, yet we have seen no problems with prop cavitation or ventilation. We did glass in the attaching plates so a smooth transition. Word of caution once people see it turn everyone wants to see a "donut" these are rough on the batteries I had to lag in additional stop bolts on the wake racks as they would swivel out during the radical demos. I ran it directly at the previous owners dock at 30 mph at 100 feet did a 180 didn't even come close. He said if he knew the boat would do that he would have never sold it. It's a kick.